Copolymers of alkoxy and hydroxy alkyl methacrylates and a process for their preparation

ABSTRACT

This invention relates to copolymers and provides copolymer obtainable by copolymerising (a) at least one alkoxy alkyl acrylate or methacrylate with (b) at least one hydroxy alkyl acrylate or methacrylate or at least one different alkoxy alkyl acrylate or methacrylate and optionally with a minor amount of a further monomer. The invention also provides a process for making such copolymers.

United States Patent Seymour et 211.

July 1975 COPOLYMERS OF ALKOXY AND HYDROXY ALKYL METI-IACRYLATES AND A PROCESS FOR THEIR PREPARATION Inventors: Donald Edwin Seymour, London;

Nicholas Mario Da @osta, Harlow, both of England Assignee: Hydron Limited, London, England Filed: May 10, 1973 Appl. No.: 359,045

Related US. Application Data Division of Ser. No. 867,379, Oct. 17, 1969, Pat. No. 3,780,003.

US. Cl. 260/861 E; 117/138.8; 117/145; 117/155; 117/161; 260/8072; 260/8073; 260/8075; 260/8076; 260/8081 Int. Cl. COSf 15/16 Field of Search 260/8075, 8076, 86.1 E, 260/8072, 80.73, 80.81

[5 6] References Cited UNITED STATES PATENTS 2,412,476 12/1946 Semegen 260/861 E 2,588,398 3/1952 Mast et a1. 260/861 E 2,594,560 4/1952 Howard 260/861 E 3,577,518 5/1971 Shepherd et 31.. 424/47 3,784,540 1/1974 Kliment et a1 1. 260/861 E Primary Examiner-Harry Wong, Jr.

2 Claims, No Drawings COPOLYMERS OF ALKOXY AND HYDRQXY ALKYL METHACRYLATES AND A PROCESS FOR THEIR PREPARATHON This is a division. of application Ser. No. 867,379. filed Oct. 17, 1969, and now US. Pat. No. 3,780,003. The present invention relates to novel copolymers.

According to the present invention there is provided a copolymer obtainable by copolymerising (a) at least one alkoxy alkyl acrylate or methacrylate with (b) at least one hydroxy alkyl acrylate or methacrylate or at least one different alkoxy alkyl acrylate or methacrylate and optionally with a minor amount of a further monomer.

Where reference is made throughout the specification and claims to alkoxy alkyl acrylates and methacrylates, the alkoxy groups present are unbranched.

Preferably the minor amount of further monomer is no more than 10% by volume based on the total volume of monomers.

Where reference is made to the optional use of a fur ther monomer it is to be appreciated that more than one such further monomer may be used if desired.

Preferred further monomers are acrylic acid, methacrylic acid, acrylamide, monoand diacrylates of gly cols and poly glycols, (e.g. glycerol and polyalkylene glycols), monoand dimethacrylates of glycols and polyglycols (e.g. glycerol and polyalkylene glycols), glycidyl acrylates and glycidyl methacrylates.

The further monomer or monomers may be present as an impurity in the major constituents of the reaction mixture or may be specifically added e.g. to provide for cross-linking.

Where the copolymer is one obtainable by reaction of an alkoxy alkyl acrylate or methacrylate with a different alkoxy alkyl acrylate or methacrylate it may be preferred that no monomers are present other than alkoxy alkyl acrylates or methacrylates and polymers thereof. It is to be understood that a minor amount of an alkyl ester of the free acid may be present as an impurity.

The copolymers of the present invention may be used to make both films and coatings which are moisture vapour permeable and gas permeable (preferably air permeable). The properties of the film or coating may be varied by varying the proportions of the ingredients used to make the copolymer.

The preferred hydroxy alkyl acrylates and methacrylates are hydroxy ethyl methacrylates (HEMA), hydroxy propyl acrylate (l-lPA) and hydroxy propyl methacrylate (HPMA).

Where hydroxy alkyl acrylates and methacrylates are used (e.g. HEMA) it may be desirable to use no more than 90% by volume of the hydroxy monomer.

Preferred alkoxy alkyl acrylates and methacrylates are ethoxy ethyl methacrylate (EEMA) and methoxy ethyl methacrylate (MEMA).

A preferred alkoxy alkyl methacrylate/alkoxy alkyl methacrylate copolymer is one obtainable by copolymerising EEMA and MEMA.

The hydroxy and alkoxy groups are usually not attached to the carbon atom of the alkyl groups connected to the oxygen groups of the ester linkage. For example the HEMA used is usually 2-hydroxy ethyl methacrylate, the MEMA used is usually 2- methoxyethyl methacrylate, the HPA used is usually Z-hydroxy propyl acrylate, the EEMA used is usually 2-ethoxyethylmethacrylate, and the HPMA used is usually 2-hydroxypropylmethacrylate.

Other monomers which have been found to be useful include 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, methoxymethyl methacrylate, ethoxymethyl methacrylate and 2-butoxyethyl methacrylate.

As mentioned above the properties of the copolymers will vary depending on the proportions of the various ingredients used to make up the copolymer. For example in copolymers involving hydroxy alkyl acrylates or methacrylates a high proportion of alkoxy alkyl acrylate or methacrylate (e.g. EEMA) gives flexible, high moisture vapour permeable, non water-swellable films at 20C., whereas a high proportion of a hydroxy alkyl methacrylate (e.g. HEMA) gives high moisture vapour permeable, brittle, water-swellable films (properties at 20C.) For example, a copolymer made up from by volume EElVlA and 20% by volume HEMA is flexible and is negligably swollen by water, whereas a copolymer made up from 50% by volume EEMA and 50% by volume HEMA is brittle and is swollen by water.

Copolymers of ethoxy ethyl methacrylate (EEMA) and methoxy ethyl methacrylate (MEMA) and containing a high proportion of MEMA will tend to be stiff and brittle (especially at temperatures in the region of 5C) whereas similar copolymers containing a large proportion of EEMA will be flexible.

The present invention also provides a process for the production of a copolymer which comprises copolymerising, in an inert atmosphere, (a) an alkoxy alkyl acrylate or methacrylate with (b) an hydroxy alkyl acrylate or methacrylate or a different alkoxy alkyl acrylate or methacrylate and optionally with a minor amount of a further monomer.

A free radical initiator, preferably a catalyst, for example, tertiary butyl peroctoate may be used. The reaction may be performed in a solvent, preferably by refluxing in an inert CO or N; atmosphere for 8 hours. Preferred solvents for polymerisations involving hydroxy alkyl acrylates or methacr'ylates are for example ethyl acetate, industrial methylated spirits, ethanol, methanol or dimethyl formamide. Preferred solvents for polymerisations not involving hydroxy alkyl acrylates or methacrylates are for example ethyl acetate, toluene, dimethyl formamide or an isopropyl/water mixture.

The copolymer may be precipitated by pouring into a nonsolvent such as petroleum ether.

Alternatively, the reaction may be taken almost to completion i.e. almost all of the monomer converted to polymer by refluxing, e.g. for 24 hours, to give a solution of the copolymer.

Films may be formed from the solution of the copolymer by casting a solution of the copolymer onto a smooth surface, for example release coated silicone paper or cast polypropylene, drying and stripping the film off the smooth surface.

To improve strength characteristics the copolymers may be self cross-linked by heating or may be cross linked by the addition of a cross-linking agent or a catalyst. A copolymer of 80% by volume lEElVlA and 20% by volume ll-lEMA may be self cross-linked by heating at C for 1 hours or longer in air atmosphere.

The films and coatings produced from the copolymers of the invention are transparent but if desired they I may be pigmented.

The new copolymers may be used as films and coatings in adhesive, medical and surgical dressings and bandages, decorative nail coatings, surgical drapes, surface adhesive suture strips, nail varnishes, cosmetics such as eye liners and plastic dressings.

The present invention will now be further described with reference to the following examples:

EXAMPLE 1 80 mls. of EEMA, 20 mls. of HEMA, 0.3 grams of tertiary butyl peroctoate and 200 mls. of ethyl acetate 20 were refluxed in a flask over a steam bath for 7 hours.

TABLE l-Continued EXAMPLE by volume mby volume by volume by volume EEMA MEMA HEMA HPMA Using gel permeation chromatography techniques,

' molecular weight measurements of the polymer of Ex- (i-e. weir'ht riverrir'cmolecular wei lzt (number average molecular weight ample were obtained. These results were:

M (i.e. modal value of molecular weight) (1.9. modal value of molecular weight) 150,000

3 J: 3 This ratio indicates the 111 weirht. dispersion.

The properties of 0.001 inch films of these polymers are set out in Table [1:

The reflux was carried out under an inert carbon dioxide atmosphere and the mixture was continuously stirred. The resulting copolymer was precipitated by pouring the mixture into petroleum ether, filtering, washing the residue and drying at 50C. A yield 80 grams of copolymer was obtained.

The above procedure was repeated, but instead of precipitating the copolymer the polymerisation was completed by refluxing for 24 hours. A yield of 98.8 g (100% conversion) was obtained.

EXAMPLES 2-7 Using techniques as described in Example 1, copolymers were prepared using the percentages by volume of the monomers set out in Table 1:

TABLE 1 7c EXAMPLE by volume by volume by volume by volume EEMA MEMA HEMA HPMA The oxygen permeability transmission rate of the copolymer of Example 3, when measured according to BS. 2782:1965 method 514A, was found to be 3000 ml's/sq. metre/24 hrs/atms/thou thickness.

EXAMPLE 8 50 mls. of MEMA, 50 mls. of EEMA, 0.3 mls. of tertiary butyl peroctoate and 100 mls. of ethyl acetate were refluxed in an inert carbon dioxide atmosphere for 24 hours. The mixture was continuously stirred. Approximately 100% conversion was obtained.

The resulting syrup (solution) was cast onto a silicone coated release paper, dried in an oven and the film removed from the release paper. The properties of the film are set out in the Table below.

Using gel permeation chromatography techniques, molecular weight measurements of the polymer of this example were taken.

The results obtained were M,,,,,, 300,000 E71,,

EXAMPLES 9 and 10 The method of Example 8 was repeated first using 60 mls. of MEMA and 40 mls. of'EEMA (Example 9) and secondly using mls. of MEMA and 30 mls. of EEMA (Example 10). The properties of 0.001 inch of these films are set out in Table Ill below.

TABLE ill EXAMPLE 71 by volume 7: by volume Moisture vapour ***Tg.(C)

EEMA MEMA permeability (gm/sqmetre/ 24 hrs. at 40C and l7z/207c relative humidity).

Film squares (0.001 inch thick) were dried in a dessicator containing CaCl weighed and then immersed in water for 24 hrs at C. The samples were then removed. excess water removed with blotting paper and weighed.

" Measured by the Payne cup method:

10 mls. of distilled water are added to the cup. A 2 /4 inches diameter sample of the material to be tested (previously conditioned by storage at 20C and 65% relative humidity for at least 8 hours) is clamped over the opening of the cup. The arrangement is then placed in an air circulating oven maintained at 40C and a relative humidity of 20% for 24 hours. There is a differ ence in relative humidity between the two sides of the sample. inside the cup the relative humidity is 100% and outside the cup the relative humidity is 20%. The loss of water from the cup is measured by weighing. The moisture vapour permeability of the sample is expressed as gms/sq.metre/24 hours at 40C and l007z/207c relative humidity.

By multiplying the result obtained by the thickness of the sample (in thousandths of an inch) a rough approximation may be obtained for the moisture vapour permeability per thousandth of an inch thickness of the sample. This is only applicable to fairly thin samples however.

*Cdass transition temperatures. The glass transition temperature is the temperature below which the polymer is brittle. The higher the Tg therefore the more brittle the polymer.

Parts by volume The above ingredients were mixed at room temperature, heated to 60C to initiate polymerisation and allowed to cool. A transparent cross-linked gel was obtained.

EXAMPLE 12 A number of 0.001 inch thick films were made by casting from solutions of various copolymers of the in- TABLE lV COPOLYMER FILM Yield point 7: Elongation (g/0.00l") at break 9O: 10 MEMA HEMA l020 80 20 EEMA HEMA 440 50 :50 MEMA EEMA 200 70 3O MEMA EEMA 290 200 The EEMA used in the examples contained 2-ethoxy ethyl methacrylate for the most part together with a very small proportion of methyl methacrylate as an impurity.

The l-lEMA used in the examples contained 2- hydroxy ethyl methacrylate for the most part, together with a small amount of di-ethylene glycol monomethacrylate, ethylene glycol dimethacrylate and methacrylic acid as impurities.

The MEMA used in the examples contained 2- methoxy ethyl methacrylate for the most part, together with a very small proportion of methyl methacrylate as an impurity.

The i-iPlVlA used in the examples contained for the most part 2-hydroxypropyl methacrylate.

We claim:

l. A copolymer prepared by copolymerizing in the presence of a free-radical initiator (a) 90 to 50 parts by volume of an alkoxy alkyl methacrylate selected from the group consisting of ethoxy ethyl methacrylate and methoxy ethyl methacrylate with (b) from 10 to 50 parts by volume of a hydroxy alkyl methacrylate selected from the group consisting of hydroxy ethyl methacrylate and hydroxy propyl methacrylate and optionally with a minor amount of a further monomer.

2. A film or coating made from a copolymer as claimed in claim ll.

UNITED STATES PATENT OFFICE CERTIFICATE OF QORRECTION Patent No. 5,895,988 Dated July 8 1975 Inventor(s) Donald Edwin Seymour et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claims priority of British Provisional Applications Non.

mom/68, filed October 22, 1968 and NO 6O75 L/68 filed December 20, 1968.

Signed and Scaled this twenty-third D a )1 0f December 19 75 [SEAL] Arrest.-

RUTH- C. M AHSON E C. MARSHALL DANN Atrestmg ()jjzcer (ommissimwr oj'Patents and Trademarks 

1. A COPOLYMER PREPARED BY COPOLYMERIZING IN THE PRESENCE OF A FREE-RADICAL INITIATOR (A) 90 TO 50 PARTS BY VOLUME OF AN ALKOXY ALKYL METHACRYLATE SELECTED FROM THE GROUP CONSISTING OF ETHOXY METHACRYLATE AND METHOXY ETHYL METHACRYLATE WITH (B) FROM 10 TO 50 PARTS BY VOLUME OF A HYDROXY ALKYL METHACRYLATE SELECTED FROM THE GROUP CONSISTING OF HYDROXY ETHYL METHACRYLATE AND HYDROXY PROPYL METHACRYLATE AND OPTIONALLY WITH A MINOR AMOUNT OF A FURTHER MONOMER.
 2. A film or coating made from a copolymer as claimed in claim 